The script combine.sh creates an amalgamated C++ source file that can be used with or without basisu_transcoder.h. This isn't a header-only file but it does offer a similar level of simplicity when integrating into a project.
Create basisu_transcoder.cpp from the transcoder sources using:
cd basis_universal/contrib/single_file_transcoder ./combine.sh -r ../../transcoder -o basisu_transcoder.cpp basisu_transcoder-in.cpp
Then add the resulting file to your project (see the example files).
If certain features will never_ be enabled, e.g. BASISD_SUPPORT_BC7_MODE6_OPAQUE_ONLY, then combine.sh can be told to exclude files with the -x option:
./combine.sh -r ../../transcoder -x basisu_transcoder_tables_bc7_m6.inc -o basisu_transcoder.cpp basisu_transcoder-in.cpp
Excluding the BC7 mode 6 support reduces the generated source by 1.2MB, which is the choice taken in basisu_transcoder-in.cpp and used in the examples, with create_transcoder.sh running the above script, creating the final basisu_transcoder.cpp.
The combiner script can also generate separate amalgamated header and source files, using the -k option to keep the specified inline directive, and -p to keep the #pragma once directives in the header:
./combine.sh -r ../../transcoder -o basisu_transcoder.h -p ../../transcoder/basisu_transcoder.h ./combine.sh -r ../../transcoder -x basisu_transcoder_tables_bc7_m6.inc -k basisu_transcoder.h -o basisu_transcoder.cpp basisu_transcoder-in.cpp
Note: the amalgamation script will run on pretty much anything but is extremely slow on Windows with the bash included with Git.
Because all it now takes to support Basis Universal is the addition of a single file, two if using the header, with no configuration or further build steps (the out-of-the-box defaults tailor the included formats for various platforms).
The library is small, adding, for example, around 250kB to an Emscripten compiled WebAssembly project (with transcoding disabled for BC7 and ATC; disabling ASTC will remove a further 64kB, and gzip will approximately half the wasm file).